In recent years, as resinification in the optical material and electronic material fields proceeds, accompanied by a demand for a decrease in size and weight, and increase in density of electronic instruments, resins excellent in heat resistance, mechanical strength, moisture absorption resistance, dimensional stability, solvent resistance and the like, as well as optical transparency, have been desired. For example, in liquid crystal display devices in which glass substrates have hitherto been used, plastic substrates have recently been used for weight saving and a reduction in breakage in dropping. However, materials used are required to have extremely high heat resistance, in respect to their production process.
As plastic materials having high transparency, heat resistance and the like as described above, cyclic olefin polymers have been proposed. As the cyclic olefin polymers, there have hitherto been proposed hydrogenated ring-opening polymers (Japanese Patent Laid-open Publication (Sho) 60-26024, Japanese Patent No. 3050196, Japanese Patent Laid-open Publication (Hei) 1-132625, Japanese Patent Laid-open Publication (Hei) 1-132625, etc.), addition copolymers of cyclic olefins and ethylene [Japanese Patent Laid-open Publication (Sho) 61-292601, Makromol. Chem. Macromol. Symp. Vol. 47, 83 (1991), etc.], addition copolymers of cyclic olefins (Japanese Patent Laid-open Publication (Hei) 4-63807, Japanese Patent Laid-open Publication (Hei) 8-198919, Published Japanese Translation of PCT Application (Hei) 9-508649, Published Japanese Translation of PCT Application (Hei) 11-505880, etc.) and the like.
Of these, the hydrogenated ring-opening polymers are not necessarily satisfactory in respect to heat resistance, because it is difficult to achieve a glass transition temperature of 200° C. or higher. Further, double bonds not hydrogenated often remain in trace amounts in molecular chains, which causes the problems of coloring at high temperatures and the like in some cases.
Many addition copolymers of cyclic olefins, obtained by metallocene catalysts using zirconium, titanium and the like are reported. It is also reported that insoluble, infusible cyclic olefinic addition polymers are obtained by the metallocene catalysts. However, the metallocene catalysts exhibit only extremely low polymerization activity on polar group-containing monomers, so that the introduction of polar groups is difficult. Further, in order to obtain high polymerization activity, catalyst components demand complicated structures, and multistep synthesis are required. Moreover, large amounts of aluminoxane are necessary as a cocatalyst. Accordingly, cost associated with the catalysts rises, and complicated processes have been required for removal of the catalysts.
In contrast, addition polymers of cyclic olefins polymerized using late transition metal compound components such as nickel and palladium can exhibit glass transition temperatures exceeding 200° C., and suitably used for applications requiring extremely high heat resistance. Further, it is possible to control the glass transition temperature or to impart functions by selection of monomer components.
As a problem in the addition polymerization of cyclic olefins, it is mentioned that polar substituents act as poisons to transition metal catalyst components to significantly decrease polymerization activity. A problem is therefore encountered with regard to the introduction of the polar groups into the addition polymers.
Japanese Patent Laid-open Publication (Hei) 4-63807 discloses a method for producing a norbornene-based polymer using a catalyst containing a transition metal compound and an aluminoxane as main components. In this specification, not only a hydrocarbon group, but also an oxygen atom- or nitrogen atom-containing group is specified as a substituent for a norbornene-based monomer. However, such a monomer is not used in examples, so that there is no description that a polymer containing a cyclic olefin having a polar group as a structural unit is obtained by the method of this specification. Further, it is apparent from the examples described in this specification that the method of this specification requires the aluminoxane component in large amounts.
Japanese Patent Laid-open Publication (Hei) 8-198919 proposes an addition type copolymer of norbornene and substituted norbornene. However, the substituent is limited to a hydrocarbon group, and a polymer containing a substituted norbornene having a polar group as a structural unit is not described at all.
On the other hand, many investigations have hitherto been conducted with respect to polymerization of cyclic olefins having a polar group. For example, W. Risse et al. [Makromol. Chem. 193, 2915 (1992), Macromolecules 29, 2755 (1996), etc.] and M. Novak et al. [Macromolecules 28, 5396 (1995), etc.] has proposed several palladium compounds. Further, Published Japanese Translation of PCT Application (Hei) 11-505880 also discloses a polymerization method of a functional group-containing norbornene type monomer using a palladium compound component.
However, the palladium catalyst systems mentioned above require multistep synthetic pathways or combinations of expensive reagents such as silver compounds in many cases, resulting in extremely increased cost with respect to the catalysts. Further, a halogenated hydrocarbon such as dichloromethane or chlorobenzene, nitromethane, tetramethylurea and the like are used as solvents, because the solubility of the catalyst components in hydrocarbon solvents is low and the polymerization activity is low. However, these solvents are expensive, or adverse effects on the human body or the environment are feared. Accordingly, they are not industrially actual solvents.
In contrast, according to PCT International Application Patents WO 97/33198 and WO 99/14635, a cyclic olefin having a polar group such as an ester group can be polymerized by a single-component catalyst system comprising a bis(perfluorophenyl)nickel complex. The nickel compounds used in these specifications also require multiple steps for synthesis, and catalyst cost rises.
That is to say, it has hitherto been desired to obtain an addition polymer containing a structural unit derived from a cyclic olefin having a polar group, using a catalyst high in availability and low in cost, without using a large amount of an aluminoxane cocatalyst. However, conventional techniques have been insufficient.
As another problem in the addition polymerization of the cyclic olefin, chain transfer dosen't occur easily and the controlled molecular weight of the addition polymer is difficult to obtain. For example, when the molecular weight of the cyclic olefin-based addition polymer is too high, difficulty in forming or damaged suraface smoothness is caused by the handling difficulty from the increased solution viscosity, insolubility in a practical solvent or a gel-like by-product component. On the other hand, in the case of the addition polymer having a low molecular weight, a formed film becomes brittle, and further, solvent resistance and liquid crystal resistance are reduced.
To control the molecular weight of the addition polymer, control of the amount of a polymerization catalyst and the addition of a molecular weight modifier has been utilized. Of these, the method by the control of the amount of the catalyst is not practical, because a large amount of the catalyst is required depending on the target molecular weight, resulting in increased cost, and great cost is necessary for reducing residual metal components to a degree required for an optical or electron material application. Further, a large amount of the catalyst makes it difficult to control the polymerization temperature.
A method is disclosed in which an α-olefin is used as a chain transfer agent for controlling the molecular weight of a norbornene functional addition polymer, in a system in which a group VIII transition metal compound is used as a polymerization catalyst (Published Japanese Translation of PCT Application (Hei) 9-508649). In this method, it is presumed that chain transfer occurs by insertion of the α-olefin and the subsequent β-hydrogen elimination mechanism, and an olefinic unsaturated bond is formed in a terminal group moiety of the norbornene-functional olefinic addition polymer. However, in this specification, the chain transfer agents available are limited, and an aromatic vinyl compound such as styrene is apparently excluded. It is therefore unable to selectively introduce an aromatic substituent into a molecular chain terminal of the polymer by this technique.
Further, Published Japanese Translation of PCT Application (Hei) 11-505877 discloses copolymerization of a norbornene type monomer and a cationically polymerizable monomer by a catalyst containing a transition metal of the group VIII. In this specification, however, an aromatic vinyl compound is excluded from both the cationically polymerizable monomer and the chain transfer agent.
On the other hand, it is reported that an aromatic vinyl compound is copolymerized with a cyclic olefin by a specific polymerization catalyst. For example, Japanese Patent Laid-open Publication (Hei) 1-311109 discloses a process for producing a copolymer of a norbornene-based monomer and styrenic monomer, using a catalyst formed of hydrocarbon—soluble vanadium and organic aluminum. Further, Japanese Patent Laid-open Publication (Hei) 4-45113 discloses a method for producing a copolymer, using a catalyst containing a nickel compound and an aluminoxane as main components. That is to say, in any of the specifications, the styrenic monomer is one of units constituting the polymer, and introduced into a molecular chain of the polymer. As a method for controlling the molecular weight, the use of hydrogen is suggested. However, it is neither described nor suggested that an aromatic vinyl compound is used for the control of the molecular weight.
Further, in Japanese Patent Laid-open Publication (Hei) 4-45113 described above, not only a hydrocarbon group, but also an oxygen atom-containing group or a nitrogen atom-containing group is specified as a substituent—for a norbornene-based monomer. However, such a monomer is not used in examples. There is therefore no description that a copolymer containing a norbornene structural unit having a polar group is obtained by the method of this specification. Furthermore, the substituent specified on the styrenic monomer in this specification is limited to a hydrocarbon group and a halogen atom, and a method for introducing aromatic group having a polar group into a polymer is not described.
Japanese Patent Laid-open Publication 2001-19723 discloses a method for producing a copolymer of a cyclic olefin and styrene into which an ionic dissociation group is introduced. However, the method of this specification comprises the step of previously producing a copolymer of the cyclic olefin and styrene and the step of introducing the ionic dissociation group such as a sulfonic acid group into the copolymer, so that polar groups that can be introduced into an aromatic substituent are limited to some of them. Further, also in this specification, styrene is regarded as a monomer. It is therefore unable to control the molecular weight with a polymerization catalyst used in examples, and it is also unable to selectively introduce an aromatic substituent into a terminal of a molecular chain.
As apparent from the above, it has been unable to control the addition polymer of the cyclic olefin to an arbitral molecular weight, and to selectively introduce the aromatic substituent into the molecular chain terminal by the conventional techniques. Similarly, it has also been unable to introduce the polar group-containing aromatic substituent into the molecular chain terminal of the cyclic olefinic addition polymer.
Further, in any of the specifications mentioned above, a cyclic nonconjugated diene as a mean for molecular weight control and activity enhancement is neither described nor suggested. Furthermore, a technique for controlling the molecular weight distribution of the cyclic olefinic addition polymerization has not hitherto been reported, including the above-mentioned specifications.